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A new study published this month in STEM CELLS Translational Medicine indicates that treating heart patients with mesenchymal stem cells (MSCs) does not increase their risk of irregular heart beat (arrhythmia). In fact, the MSCs had the opposite effect and showed promise of improving the condition.


“This could be an important breakthrough for many heart patients, as proarrhythmia – which is a new or more frequent occurrence of pre-existing arrhythmia – unfortunately can be a side effect of some of the drugs we’re using to treat these patients,” said the study’s lead author, Raul Mitrani, M.D., of the University of Miami School of Medicine’s Division of Cardiology (Miami, Florida).


Arrhythmia is a common condition resulting when electrical impulses in the heart do not work properly, causing the heart to beat either too fast, too slow or erratically. This in turn interferes with blood flow throughout the body and can potentially damage or shut down organs. While some experience no symptoms and their arrhythmia is harmless, in others it can be life threatening. Treatments include anti-arrhythmic drugs; implantable devices such as a pacemaker; surgery; or catheter ablation (a procedure that uses radiofrequency energy to destroy a small area of heart tissue that is causing the off-kilter beats).


As more studies are showing the potential of stem cells to repair damage caused by heart disease, Dr. Mitrani and his colleagues at UM wondered whether the stem cells – specifically MSCs, which are ‘adult’ stem cells that can produce more than one type of specialized cell of the body – would follow the path of some of the anti-arrhythmia drugs and worsen the condition. Previous studies had indicated that perhaps was the case with certain other types of stem cells, but no studies had focused on MSCs.


To find the answer, they analyzed the results of 88 patients enrolled in two clinical trials testing the potential of MSCs in treating ischemic cardiomyopathy. This is a common condition in which the heart’s ability to pump blood is decreased because its main pumping chamber, the left ventricle, is enlarged, dilated and weak. The patients had an average age of 61 years and were divided into groups treated with either MSCs, bone marrow stem cells (BMCs) or placebo.


A year after their treatments, those who received MSCs all showed no signs of arrhythmia. “We were encouraged by what we saw,” Dr. Mitrani said. “Even better, in a group of patients with low ventricular ectopy burden – what some call ‘heart hiccups’ or ‘skipped beats’ – there were definite signs of improvement while in the BMC and placebo groups, no similar signal for improvement was noted.

“This leads us to believe that prospective studies might clarify the role of MSCs to reduce ventricular arrhythmias.”


“By combining data from two studies, the authors were able to study this question in one of the largest groups of patients to date,” said Anthony Atala, Editor-in-Chief of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine. “These findings are important because they emphasize the need for further large prospective studies to evaluate the anti-arrhythmic potential of mesenchymal and other newer cell-based therapies.”


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